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Wednesday, 19 October 2011

Wireless charger can restore vehicles' batteries on the move

The EngineerOct 18, 2011

Wireless-charging technology could enable different electric vehicles to replenish their batteries using the same infrastructure while moving.

Canadian railway manufacturer Bombardier is testing wireless charging pads located underneath roads that could theoretically allow electric cars, trucks, buses and trams to travel without ever needing to stop and recharge.

Previous wireless-charging technology has been designed primarily for stationary charging, but Bombardier’s research has focused on moving vehicles of different sizes, in particular, public transport that follows a regular route and stopping pattern.

For buses and trams, charging points are placed at route stops where the vehicle can receive its largest charge while passengers get on and off. Then it progresses to the next stop, passing over several more charging points and topping up as it moves.

‘Typically there are about 300m to 500m between two stops on the routes,’ Christian Köbel, director of product management for the Primove technology.

‘This allows regular traffic so you can plan a regular schedule. That’s why we can reduce the size of the storage significantly because we know exactly what the vehicle will do.’

With suitable battery technology, which Bombardier is currently investigating, buses could reduce their charging times to every two or three stops, although this is less of a possibility for trams as they are much heavier.

Electricity is transferred from the buried charging point to corresponding technology underneath the vehicle using magnetic induction. As the vehicle drives over the charger its sends out a radio signal to identify itself and prove that it is authorised to use the station.

The charging point only engages when it is completely covered and shielded by the vehicle, meaning pedestrians and passengers aren’t exposed to its magnetic fields.

As it is designed for use by a range of different moving vehicles, the technology also has a built-in flexibility that allows it to provide charge even if the vehicle isn’t perfectly aligned on top of it.

‘The biggest challenge was applying a technology that is mostly used for very small power ranges and scaling it up to a complete road traffic and public transport use, from typical 3.3kW applications to 160–200kW charging.’ said Köbel.

‘A significant part in that is dealing with the power requirements, the emitted field, what you use in terms of components — no standard components are used because it has completely different requirements.

‘The second challenge is applying all the rail and automotive industry standards onto the technology, which is typically used in an industry that is far more relaxed.’

Primove has so far been tested on a 125m stretch of road in Lommel, Belgium, using converted hybrid buses and on a largely disused tramway in Augsburg, Germany.

Bombardier is already offering the system for tender and hopes to see it in place for buses in 2012 and for trams in 2014 due to the additional infrastructure needed to create a tramway.